A position sensor is a device that can detect the presence and location of a touch, by a user's finger or by an object, such as a stylus, for example, within a display area of the position sensor overlaid on a display screen. In a touch sensitive display application, the position sensor enables a user to interact directly with what is displayed on the screen, rather than indirectly with a mouse or touchpad. Position sensors can be attached to or provided as part of computers, personal digital assistants (PDA), satellite navigation devices, mobile telephones, portable media players, portable game consoles, public information kiosks, and point of sale systems etc. Position sensors have also been used as control panels on various appliances.
There are a number of different types of position sensors/touch screens, such as resistive touch screens, surface acoustic wave touch screens, capacitive touch screens etc. A capacitive touch screen, for example, may include an insulator, coated with a transparent conductor in a particular pattern. When an object, such as a user's finger or a stylus, touches or is provided in close proximity to the surface of the screen there is a change in capacitance. This change in capacitance is sent to a controller for processing to determine the position of the touch on the screen.
In recent years, touch sensitive position sensors have been used in large screens, such as tablet PC's. When a user interacts with large touch screens, they may often inadvertently touch the screen, such as with one or more fingers and/or the palm of the hand while writing on the screen with a stylus. Even when intending to touch the screen with only an index finger, a user may also touch the screen with another finger or another part of the hand. Detection of an inadvertent, unintended, accidental, or otherwise non-purposeful touch may lead to a device operation or response that is different from what would have occurred had the user touched only the intended position of the touch screen.